Lomachaeta Mickel

Lomachaeta Mickel 1936: 289 . Type species: Lomachaeta hicksi Mickel, by original designation.

Diagnosis. Males of the genus Lomachaeta can be distinguished from other Sphaeropthalmina by the presence of an apical row of stout, lanceolate bristles on metasomal segments 2–5, which are directed obliquely inwards (Fig. 1). Females of this genus can be distinguished from other Mutillidae by the following combination of characters: presence of subovate eyes, presence of a reticulated surface on the head and mesosoma (Fig. 5), absence of carinae defining the lateral margins of the pygidial area, presence of apically edentate mandibles, a petiolate first metasomal segment (Fig. 5), and presence of tuberculate propodeal spiracles (Fig. 5).

The following additional characters will help differentiate Lomachaeta from other Sphaeropthalmina: males having a tridentate mandible with a ventral tooth or slight excision that is angulate medially, lacking parapsidal lines and notauli, having an inconspicuous pterostigma (Fig. 2), having a distinctly petiolate first metasomal segment, having a hypopygium that is rounded apically but bidentate medially, having reduced wing venation in comparison with other New World species (Fig. 2), and having the cuspis reduced to a knob­like structure (Figs. 14–22); females having a genal carina and a pyriform mesosoma (widest anteriorly and gradually narrowing posteriorly) (Fig. 5).

The genitalia of male Lomachaeta are of limited taxonomic use because they are quite similar between species (Figs. 3,4, 14–22). The genitalia, however, along with the presence or absence of a ventral mandibular tooth, do suggest several relationships. The following three species groups are defined by male characters: L. crocopinna species­group, L. hicksi species­group and L. hyphantria species­group.

The L. crocopinna species­group is defined by lack of the ventral mandibular tooth, presence of distinctly brachyplumose pubescence, and presence of long setae on the ventral margin of the parameres (Figs. 19, 20), and includes L. crocopinna, sp. nov. and L. ptilohyalus, sp. nov.

The L. hyphantria species­group is defined by the lack of the ventral mandibular tooth, presence of indistinct brachyplumose pubescence (serrate), presence of confluent punctures on the mesonotum (Fig. 13), and absence of long setae on the ventral margin of the parameres (Fig. 21), and includes only L. hyphantria, sp. nov.

The L. hicksi species­group is defined by presence of a ventral mandibular tooth, presence of indistinct brachyplumose pubescence (serrate), and absence of long setae on the ventral margin of the parameres (Figs. 14–18, 22) and includes L. chionothrix, L. cirrhomeris and L. hicksi .

The males of L. argenta, L. ibarrai, and L. vianai remain unknown. As such, this species are not placed into species­groups, because the species­groups defined above are based on characters derived from males.

Hosts. Host data suggests that Lomachaeta species are opportunistic parasitoids. Rearing parasitoids from twig and trap nests provided new host records for four more species of Lomachaeta . Host data suggests that the species may be limited to cavity nesting hosts of small size, including Solierella Spinola, Pisonopsis Fox and Trypoxylon Latreille. Specific hosts are listed under each Lomachaeta species. It is noteworthy that the females of the species­group lack a distinct pygidium, as do many twig nesting sphecoid wasps, bees, and their hymenopteran parasitoids, such as mutillid species of the Sphaeropthalma uro species­group.

Distribution. Lomachaeta ranges throughout the United States, south to Guatemala, and is also found in Argentina and Bolivia. It is likely that Lomachaeta occurs along with its hosts throughout the Neotropics.